It is known that a diamond chip and certain other insulators and certain semiconductors can be made to conduct electricity through bombardment with an electron beam or laser radiation and become an insulator soon after the bombardment stops. The time between the termination of the bombardment and the change in the property of the material from conductor to insulator is measured by a parameter known as the "free carrier lifetime". In some materials this time is extremely short. For example, the free carrier lifetime for radiation-damaged silicon-on-sapphire is 0.6 pico seconds. (See Darrow et al, "Optics Letters", Vol. 15, No. 6, Mar., 15, 1990.)
It is well known that an electron beam can be forced to trace out various paths including an elipsoidal path on a surface generally perpendicular to the beam by subjecting the beam to a varying the electric field.